Excavation tools of the types described herein are typically mounted to conventional excavators or backhoes having a dipper stick, with the tool mounted on the dipper stick. The tools are employed for excavation of difficult-to-excavate intermediate substrate, e.g. substrate between the category of loose soil or loose gravel and the category of solid rock. Attempts have been made to develop tools that are effective and efficient in excavating intermediate substrate. For example, an excavation tool for the removal of substrate is described in Horton U.S. Pat. No. 7,739,815, and a multi-tooth bucket approach where several teeth are mounted on the back side of a bucket is described in Arnold U.S. Pat. Nos. 4,279,085 and 4,457,085. The complete disclosures of all of these references are incorporated here by reference. Each of these approaches has been found to have drawbacks, and none is seen to be particularly efficient or effective for excavation of intermediate substrate with high production, wide width, high capacity buckets.